Rotating connector for operative connection between a buoy and a floating vessel for the production of hydrocarbons

ABSTRACT

A rotating connector or coupling device for interconnection between at least one fluid passage (9) through a submerged buoy (1, 2) and a pipe system on a floating vessel for the production of hydrocarbons, comprising a pair of cooperating, fluid-transferring swivel members in the form of a female member (3) and a male member (4) which may be introduced axially into or withdrawn from each other, the female member (4) being permanently fixed to the buoy (1, 2), and an electrohydraulic swivel (30) which is arranged on the top of the male swivel member (4) and comprises partly a slip-ring arrangement (37, 45) for the transfer of high electric power and electrical/optical control signals, and partly a number of hydraulic courses for the transfer of hydraulic signals. The female and male swivel members (3, 4) include cup-like housing members (60, 61) which are insertable into each other and which, at their lower ends, have coupling discs (62, 63) with cooperating connector parts (81, 82; 83, 84) forming past of respective underwater couplers (72, 73), the housing members (60, 61) being arranged to be filled with water, for submerged operation of the underwater couplers (72, 73).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a rotating connector for interconnectionbetween at least one fluid passage through a submerged buoy and a pipesystem on a floating vessel for the production of hydrocarbons,comprising a pair of cooperating, fluid-transferring swivel members inthe form of a female member and a male member which may be introducedaxially into or withdrawn from each other, the female member beingpermanently fixed to the buoy, and an electrohydraulic swivelconstituting a part of the male member and being arranged for transferof electrical power and electrical and hydraulic control signals, theswivel members at their lower ends comprising cooperating connectorparts for interconnection of respective power, signal and hydrauliclines from the swivel and from the buoy.

2. Discussion of the Prior Art

A rotating connector or coupling device comprising cooperating swivelmembers of the above-mentioned type for example is known from Norwegianpatent application No. 932460. This application describes a system foroffshore production of hydrocarbons by means of a vessel which isarranged for quick connection to or disconnection from a submerged buoy,where the buoy is of the type comprising a bottom-anchored centre memberwhich is connected to a number of risers extending up to the buoy, andan outer buoyancy member which is rotatably mounted on the centre memberand may be introduced and locked in a submerged downwardly openreceiving space in the vessel. At the upper end of the buoy there isarranged a rotating coupling or swivel device of the stated type,wherein the swivel members define mutually sealed annular spaces orannuluses communicating with associated fluid paths in the swivelmembers, for the transfer of process fluid and possible injection fluidsbetween the risers and a pipe system on the vessel. The female swivelmember is permanently fixed to the centre member of the buoy whereas themale member is connected to an operating means on the vessel, so thatthe swivel members may be introduced into and withdrawn from each otherby the operating means, the swivel members defining said annuluses ininterconnected condition. On each side of the annuluses there isprovided for sealing means which may be activated by means of a pressurefluid to form a seal between the annuluses, and which may be relieved incase of mutual disconnection of the swivel members.

An electrohydraulic swivel which is arranged such as stated in theintroduction, is not described in said patent application. However, suchan arrangement lately has become known in the market in connection withthe development and production of the introductorily stated connector.In the known device the electrohydraulic swivel is arranged at the lowerend of the device and is constructed for the transfer of electricalpower at intermediate voltages, i.e. of the order of 1000 volts.However, in operation of production vessels of the topical type it isdesirable to be able to transfer electrical power of a substantiallyhigher value than with the known connector, e.g. 10-12 MVA or higher.The corresponding voltage and current values in three-phase transmissionmay be about 11 kV and 600 A, or higher. An electrohydraulic swivel forthe transfer of such a high electrical power requires a larger spacethan what is allowed by the known connector. Further, the knownarrangement is not so flexible as desirable as regards the possibilityto satisfy special customer specific demands and needs. In addition, inorder to satisfy the demands to security in the topical operatingenvironment, there is a need to take special precautionary measures, inorder to avoid explosion hazard.

SUMMARY OF THE INVENTION

It is thus an object of the invention to provide a rotating connectorhaving an electrohydraulic swivel which is able to transfer highelectrical power, and wherein the construction gives a great flexibilitywith respect to user adaptation, at the same time as the construction intotal is compact and operationally safe.

The above mentioned object is achieved with a rotating connector of theintroductorily stated type which, according to the invention, ischaracterized in that the electrohydraulic swivel is arranged on the topof the male swivel member and comprises a slip-ring arrangement for thetransfer of high electrical power and control signals, and that thefemale and male swivel members comprise cup-like housing members whichare insertable into each other and have coupling discs with cooperatingconnector parts forming part of respective underwater couplers, thehousing members being arranged to be filled with water, for submergedoperation of the underwater couplers.

By placing the electrohydraulic swivel uppermost in the rotatingconnector, there is obtained a flexible arrangement making it possibleto comply with as many customer specific demands as possible, i.e. oneachieves an increased flexibility with respect to power quantity, thenumber of "consumers" which can be supplied simultaneously, etc. Bymeans of the stated structure comprising water-filled housing membersand underwater couplers there is obtained an explosion-safe arrangement,the constituent elements being kept at a low surface temperature, sothat one is secured against the danger of explosion because of ignitionof explosion-hazardous gases which may occur in the topical operatingenvironment.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described below in connection with anexemplary embodiment with reference to the drawings, wherein

FIG. 1 shows an axial longitudinal section through a buoy at the upperend of which there is arranged a rotating connector according to theinvention;

FIG. 2 shows an enlarged section of the buoy and the connector in FIG.1;

FIG. 3 shows an axial section through an embodiment of theelectrohydraulic swivel; and

FIGS. 4 and 5 show a male member and a female member, respectively, ofan underwater coupler, each of the members being shown partly in sideview and partly in longitudinal section.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The buoy shown in FIG. 1 is of the introductorily stated type whichcomprises a bottom-anchored centre member and an outer buoyancy member 2which is rotatably mounted on the centre member and is intended forintroduction and releasable securing in a submerged receiving space (notshown) in a floating production vessel. The rotating connector orcoupling device which is arranged at the upper end of the buoy,comprises a pair of cooperating swivel members in the form of a femalemember 3 which is permanently fastened to the centre member 1 of thebuoy, and a male member 4 which may be inserted axially into orwithdrawn from the female member by means of an operating means

As better shown in the enlarged view of FIG. 2, the swivel membersdefine an annular space or annulus 6 communicating with a pair of fluidpaths or fluid courses 7 in the female member 3 and a pair of fluidcourses 8 in the male member 4, for the transfer of process fluidbetween transfer pipes 9 extending through the centre member 1 of thebuoy, and a pipe system (not shown) on the vessel. As will be clear, thetransfer pipes 9 at the lower end will be connected to a riser (notshown) which is connected to the buoy. In the shown embodiment there areused two parallel fluid paths in order to achieve a sufficient flowcapacity with a reduced diameter of the fluid courses 8 as compared tousing a single course through the male swivel member.

As will be appreciated, the shown exemplary embodiment is intended forthe case wherein only one process fluid is to be transferred through theconnector. When several fluids are to be transferred, for instance whenwater injection in the topical reservoir is necessary, the connectorwill be provided with a number of annuluses, fluid courses and sealingmeans which correspond to the topical need.

As appears from FIG. 1, in the centre member of the buoy there is alsoarranged a pipe stretch 10 debouching into a flange connection at theupper end of the buoy. This pipe stretch is arranged for piggingpurposes, for introduction of a pig into the riser which is connected tothe buoy, for inspection or maintenance purposes. The pigging pipe 10 aswell as the transfer pipes 9 are provided with closing valves 11 whichcan be operated by means of hydraulic actuators 12.

On each side of the annulus 6 the male member 4 is provided with aperipheral annular groove receiving a radially movable ring element 13having a static sealing means for static sealing against the femaleswivel member 3, and having dynamic sealing means for sealing betweenthe ring element 13 and the side walls of the annular groove. Thesealing means can be operated hydraulically by means of a barrier liquidhaving a higher pressure then the process fluid pressure. For a closerdescription of the constructive embodiment and the manner of operationof this arrangement reference is made to the introductorily mentionedpatent application No. 932460.

As mentioned above, the male swivel member 4 may be introduced into orwithdrawn from the female swivel member 3 by an operating means 5. Thisis in the form of a telescopic, hydraulic cylinder which is supported bya ring flange 14 to which there is fastened a guide sleeve 15 in whichthe male swivel member 4 is slidably mounted. The ring flange 14supports a protecting housing 16 receiving the male swivel member whenthis is pulled up from the female swivel member. At its upper end theprotecting housing is coupled to a crane (not shown) by means of whichthe housing 16 together with the guide sleeve 15 and the male swivelmember 4 which is pulled up into the housing, can be removed from thespace above the buoy (when this is to be introduced into the receivingspace in the vessel), or brought into position above the female swivelmember 3 when the swivel members are to be interconnected.

As appears, the female swivel member 3 at its upper end is provided witha rotatably mounted holding ring 17, whereas the lower end of the guidesleeve 15 is downwardly tapering and adapted for introduction into theholding ring 17. When the male swivel member is to be introduced intothe female swivel member, the housing 16 and the guide sleeve 15 arefirstly lowered in coarsely centred position above the female member, sothat the guide sleeve is introduced to an abutment position in theholding ring 17. Thereafter the guide sleeve is locked to the holdingring by means of locking means consisting of hydraulic locking cylinders18 which are fastened to the outer side of the guide sleeve. In thismanner there is secured an accurate positioning of the swivel membersrelative to each other, so that the male member can be introduced intoand withdrawn in a safe and gentle manner, and the dimensionaltolerances of the swivel members thereby may be kept at a minimum.

It is to be remarked that the fluid courses 8, via the shown annulus 19and the associated passage 20 through the guide sleeve 15, is connectedto said pipe system on the vessel via a flexible hose (not shown), inorder to allow the movements of the guide sleeve in connection with theabove mentioned manipulation of the male swivel member. Further, it isto be remarked that, on each side of the annulus 19, there are arrangedhydraulically operated seals 21 for static sealing between the maleswivel member and the guide sleeve when the male member has been broughtin place in the female member.

The rotating coupling device or "connector" is provided with anelectrohydraulic swivel 30 forming part of the male swivel member andbeing arranged at the top thereof, as shown in FIG. 1. This swivel hasfor its task to transfer electrical power from the production vessel tothe topical subsea installation, and moreover to transfer all necessaryelectrical and hydraulic control signals to the subsea installation. Itis also conceivable that it may be used to transfer electrical powerand/or electrical and hydraulic control signals to the vessel from otherinstallations, both at the surface and under water.

An embodiment of the electrohydraulic swivel 30 is schematically shownin longitudinal section in FIG. 3. This swivel structure is commerciallyavailable and supplied by the company Focal Technologies Inc., NovaScotia, Canada. The swivel is constructed for the transfer of highelectrical power and in the illustrated case is intended for three phasetransfer with the introductorily stated voltage and current values (11kV/600 A, i.e. approximately 11,4 MVA).

In principle, the swivel comprises a central, hollow "column member" 31which in operation is fixedly connected to the female swivel member 3and thus is stationary relative to the centre member 1 of the buoy, andan outer cover member 32 having a lower bottom plate 33 which is fixedlyconnected to a carrier flange 34 at the top of the male swivel member 4,so that the cover member in operation is stationary relative to thevessel. As shown, the cover member 32 is rotatably mounted on the columnmember 31 by means of a pair of bearings 35 and 36.

Within the cover member 32 the column member 31 is provided with aslip-ring arrangement consisting of three slip rings 37 (only one isshown) which are insulated from each other by means of intermediateinsulating rings 38. To each slip ring there is connected a power cable39 which is led down through a central passage in the column member 31and further down through the male swivel member, as further describedbelow. The power cables from the vessel are introduced into the covermember via respective curved pipe sockets 40 which are fastened to theunderside of the bottom plate 33 of the cover member with a mutualangular distance of 90°, i.e. there are four pipe sockets of which threeare used for the power cables. Only one power cable 41 is partly shown,and this is in contact with the associated slip ring 37 via a contactpiece 42.

In FIG. 3 there are not shown slip rings for electrical control signals.Instead the swivel is shown to comprise a slip-ring means 43 fortransferring fibre-optical signals. This means comprises a supportingmember 44 which is rigidly connected to the cover member 31 and which inthe illustrated case comprises a pair of fibre-optical slip rings 45.The fibre-optical lines are not shown in the Figure.

The swivel 30 is oil-filled and pressure-compensated, and the powercables entering the swivel are presupposed to be carried in oil-filledhoses. These cables in practice come from a connecting box (not shown)which, via ship cables, is coupled via a power switch to a high-voltagedistribution panel. The electrohydraulic swivel also comprises hydrauliccourses for the transfer of hydraulic signals, and also forpressurization of the aforementioned sealing means forming part of therotating connector. In the illustrated embodiment there are arrangedfour courses of which each comprises a passage 50 extending radiallythrough a cylindrical transition member 51 which surrounds the columnmember 31 and is fastened to the bottom plate 33 of the cover member,and an associated annulus and an axial passage 52 extending through thecolumn member and debauching on the underside thereof. Said courses areconnected to hydraulic lines 53 which are only suggested in dash-dotlines in FIG. 2.

As shown in FIG. 2, the female and male swivel members 3, 4 includecup-like housing members 60 and 61, respectively, which are insertableinto each other. The lower bottom parts thereof are formed as couplingdiscs 62 and 63, respectively, which are provided with cooperatingconnector members for interconnection of the cables and lines from theelectrohydraulic swivel 30 with corresponding cables and lines 64, 65extending through the centre member 1 of the buoy between the connectorsand a sea cable 66 which is terminated in a cable hanger 67 (see FIG.1).

The power cables and the different electrical and/or fibre-opticalsignal lines from the electrohydraulic swivel 30 are carried downthrough the male swivel member 4 via a cable tube 68 extending through acentral, axial passage 69 in the male swivel member 4, and which at itsupper end is rigidly connected to the lower end of the column member 31of the swivel 30. At its lower end the tube passes into a pair of hoses70 and 71 of which one hose 70 receives a power cable and is connectedto the upper part of a connector 72, whereas the other hose 71 receivessignal lines and is connected to the upper part of a connector 73. Likethe electrohydraulic swivel, the cable tube 68 as well as the hoses 70and 71 are oil-filled, the tube and hoses being in fluid connection withthe swivel.

In FIGS. 1 and 2 there is, for the sake of clearness, shown only oneconnector 72 for a power cable, even if in practice there will bearranged three hoses and connectors in the case of three-phase powertransmission for high outputs (11 kV/600 A). For lower outputs (3,3kV/125 A) a three-phase cable may be carried in each hose 70, and theconnectors will also be three-phased.

As regards the hydraulic lines 53 from the electrohydraulic swivel,these are carried through the axial passage 69 of the male swivel memberon the outside of the cable tube 68, and are connected to a hydrauliccoupler 74. These lines may also have branchings (not shown) forpressurization of the seals forming part of the rotating connector.Contact between the cooperating connector members is established whenthe coupling discs 62, 63 are moved together in a controlled manner wheninserting the male swivel member 4 in the female swivel member 3. Forensuring the correct mutual orientation of the coupling discs when theseare moved together, the side walls of the housing members 60, 61 areprovided with a guide means consisting of a lug 75 which is resilientlyarranged in the side wall of the housing member 60 and which engages ina helical groove 76 arranged in the outer surface of the side wall ofthe housing member 61. During the final part of the interconnectionmovement the coupling disc 62 is guided to the correct position by apair of guide pins (not shown) on one disc which are introduced incorresponding holes (neither shown) in the other disc. In this mannerthe correct mutual interconnection position of the connector members issecured, independent of in which position the buoy has been pulled inand locked in the receiving space of the vessel.

In the interconnected position of the swivel members 3 and 4, thehousing members 60, 61 are locked to each other via the coupling discs.In order to allow turning of the male swivel member in case of apossible turning of the vessel about the centre member of the buoy, thehousing member 61 therefore is rotatably mounted on the male swivelmember. This is achieved by means of a pair of bearings 77, 78 arrangedbetween the housing member 61 and an encircling supporting flange 79which is fastened to the lower end of the male swivel member.

As stated above, the connectors in the present arrangement consist ofunderwater couplers, with the advantages involved thereby, as stated inthe introduction. The housing members 60 and 61 thus will be filled withwater during operation. For control of the water level WL in the housingmember 61, there is arranged a water detector 80 at the upper endthereof, which detector is mounted on the lower end of the cable tube68.

The underwater couplers for the power cables and for theelectrical/optical signal cables consist of two units, viz. a plugmember which is mounted on the upper coupling disc 62, and a receptaclemember which is mounted on the lower coupling disc 63. Thus, in FIG. 2,the coupler 72 for the power cable is shown to consist of a plug member81 and a receptacle member 82, whereas the coupler 73 for theelectrical/optical control signals is shown to consist of a plug member83 and a receptacle member 84.

An embodiment of the underwater coupler 72 for power transmission isshown more in detail in FIGS. 4 and 5, wherein FIG. 4 shows the plugmember 81 and FIG. 5 shows the receptacle member 82. The shown coupleris commercially available and supplied by the British company TronicElectronic Services. Since the coupler is of a known design, only somemain elements thereof will be described.

As shown in FIG. 4, the end 85 of the cable from the electrohydraulicswivel 30 is inserted into the plug member and retained by means of acable nut 86 and a clamping sleeve 87. The stripped conductor end of thecable is retained in a terminating sleeve 88 and is in connection with asocket contact 89. The socket contact receives a so-called shuttle pin90 which is biased by a spring 91 to an outer position in which theouter end of the shuttle pin goes through a seal 92 (when the plugmember is disconnected from the receptacle member).

In the receptacle member 82 the end 93 of the cable 64 from the buoy isintroduced and retained by means of a cable nut 94 and a clamping sleeve95. The stripped conductor end of the cable is retained in a terminatingsleeve 96 and is in connection with a contact pin 97 via a contact rod98. When the plug member is introduced into the receptacle member, thecontact pin 97 is brought into engagement with the socket contact 89,the shuttle pin 90 then being pressed into the housing receiving thespring 91.

Both the plug and the receptacle member is filled with silicone gel andis pressure-compensated. For filling and venting purposes the plugmember is provided with a filling and venting screw 99, and thereceptacle member is provided with a corresponding filling and ventingscrew 100.

For radial and axial tolerance during interconnection of the couplermembers 81 and 82 these are mounted in a spring suspension meanssupplied together with the coupler. This means is schematically shown inFIG. 2 and comprises a spring-loaded disc 101 which is arranged on theplug member 81 and is mounted by means of three clamping bolts 102, onein each corner of the disc.

I claim:
 1. A rotating connector for interconnection between at leastone fluid passage (9) through a submerged buoy (1, 2) and a pipe systemon a floating vessel for the production of hydrocarbons, comprising apair of cooperating, fluid-transferring swivel members in the form of afemale member (3) and a male member (4) which may be introduced axiallyinto or withdrawn from each other, the female member being permanentlyfixed to the buoy (1, 2), and an electrohydraulic swivel (30)constituting a part of the male member (4) and being arranged fortransfer of electrical power and electrical and hydraulic controlsignals, the swivel members (3, 4) at their lower ends comprisingcooperating connector parts (81, 82; 83, 84) for interconnection ofrespective power, signal and hydraulic lines from the swivel and thebuoy, CHARACTERIZED IN that the electrohydraulic swivel (30) is arrangedon the top of the male swivel member (4) and comprises a slip-ringarrangement (37, 45) for the transfer of high electric power and controlsignals, and that the female and male swivel members (3, 4) includecup-like housing members (60, 61) which are insertable into each otherand have coupling discs (62, 63) with said cooperating connector parts(81, 82; 83, 84) forming part of respective underwater couplers (72,73), the housing members (60, 61) being arranged to be filled withwater, for submerged operation of the underwater couplers (72, 73).
 2. Arotating connector according to claim 1, CHARACTERIZED IN that, at theupper end of the housing member (61) of the male swivel member (4),there is arranged a water detector (80) for sensing of water level inthe housing member.
 3. A rotating connector according to claim 1 or 2,CHARACTERIZED IN that connecting cables (85) and lines between theelectrohydraulic swivel (30) and the underwater couplers (72, 73) arecarried through an oil-filled tube (68) which, at its upper end, isfastened to the swivel (30) and is carried through a central axialpassage (69) in the male swivel member (4), and which, at its lower end,passes into oil-filled hoses (70, 71) connected to associated underwatercouplers (72, 73).
 4. A rotating connector according to claim 3,CHARACTERIZED IN that hydraulic pipelines (53) between theelectrohydraulic swivel (30) and hydraulic connectors (74) on thecouplings discs (62, 63) are carried through the axial passage (69) ofthe male swivel member on the outside of the oil-filled tube (68).
 5. Arotating connector according to claim 1 CHARACTERIZED IN that mutuallyfacing side walls of the housing members (60, 61) are provided with ahelical guide means (75, 76) to guide the coupling disc (62) of the maleswivel member (4) to the correct position relative to the coupling disc(63) of the female swivel member (3) when introducing the male swivelmember (4) into the female swivel member (3).
 6. A rotating connectoraccording to claim 1, CHARACTERIZED IN that the electrohydraulic swivel(30) also includes a slip-ring means (43) for transferring fibre-opticalcontrol signals.